(CNN) -- A former Los Angeles police officer who police say has violently threatened his former colleagues shot at least two officers early Thursday, killing one, sparking a huge manhunt in Southern California, according to authorities.
Christopher Jordan Dorner, 33, is also wanted in a double slaying Sunday in Irvine, California.
The California Highway Patrol issued an alert Thursday morning urging officers in several Southern California counties to be on the lookout for Dorner after the overnight shootings.
Two officers in Riverside were shot, one fatally, police there confirmed to CNN. CNN affiliate KTLA reported another officer was shot in Corona, California.
Irvine police identified Dorner on Wednesday as the suspect in the February 3 deaths of Keith Lawrence and Monica Quan in Irvine.
Dorner also has made violent threats against other Los Angeles police officers, the agency said Wednesday.
"I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty," Dorner allegedly wrote in a lengthy letter promising retribution against the department, where he worked from 2005 until 2008. An LAPD source provided the document to CNN.
The letter writer claimed he was terminated for reporting excessive force by a fellow officer, and said his attacks were retribution for his termination, as well as a culture of racism and violence he says continues within the department.
He called the attacks against police "a necessary evil that I do not enjoy but must partake and complete for substantial change to occur within the LAPD and reclaim my name."
Los Angeles police warned people who encounter Dorner not to approach him, saying he is likely "armed and extremely dangerous."
"Our department is implementing all measures possible to ensure the safety of our LAPD personnel, their families and the Los Angeles community, and will continue to do so until Dorner is apprehended and all threats have been abated," police said in a statement.
CNN's Mallory Simon and Deanna Hackney contributed to this report.

Geraldo show tonight. Big damn snow in NY, Boston, Nj. Then this guy in California. Proof of rampant racism in law enforcement. And the Grammys are this week. What is the world coming to? Get this fixed so we can enjoy the Grammys!!! Damnnnnnnn.

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Frazod to KC Nitwit..."Hey, I saw a picture of some dumpy bitch with a horrible ****tarded giant back tattoo and couldn't help but think of you." Simple, Pure, Perfect. 7/31/2013

Dave Lane: "I have donated more money to people in my life as an atheist that most churches ever will."

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"Political correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t*rd by the clean end"

I don't think so. I read most of his writing and he sounds like a complete nutjob with his odes to beautiful famous women, Bill Cosby, Michelle Obama, and that strange little man Ellen Degeneres. Ramblings of somebody with some serious chemical imbalances, mania, severe narcissism, a serious invincibility complex, and a shit ton of I Me Mine going on. He's no hero, just another psycopathic famewhore.

I agree, but wow....I'm stunned about how folks are going on... I had a normal Saturday, I hope everybody else did too!

Its agreed that the LAPD has been mired in controversy for seemingly forever, and they havent done themselves any favors during this situation to be sure... but i cant buy painting them all as some kind of outta control aggression freaks bent on abusing everyones rights.

I'm sure most of them took the job for the right reasons, a job starting at maybe 40k a year that asks them to risk their lives on a daily basis.

Thats not to say there isnt corruption and bad seeds, but thats no easy job for measly money.

Its agreed that the LAPD has been mired in controversy for seemingly forever, and they havent done themselves any favors during this situation to be sure... but i cant buy painting them all as some kind of outta control aggression freaks bent on abusing everyones rights.

I'm sure most of them took the job for the right reasons, a job starting at maybe 40k a year that asks them to risk their lives on a daily basis.

Thats not to say there isnt corruption and bad seeds, but thats no easy job for measly money.

LAPD has one of the most antagonistic relationships with the population they serve compared to other police departments. LAPD also has a long history of stomping minorities (you can start with the Zoot Suit Riots for example).

Edit: That being said, most cops are out there just for a paycheck. Unfortunately, they generally don't speak up against the ones who are overly aggressive and are cops so they can bully, maim, and have power.